AHA!
That led me to the solution, thanks!
The /dev/nvme0n1p1 had the msfdata flag set, and the /dev/nvme0n1p2 had the boot and esp flags set!
Moved those to /dev/nvme0n1p1 and set the flag for /dev/nvme0n1p2 to swap, and all is well again:
$ fdisk -l /dev/nvme0n1 Disk /dev/nvme0n1: 232.89 GiB, 250059350016 bytes, 488397168 sectors
Disk model: Samsung SSD 960 EVO 250GB
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 5053CB27-A627-1B45-9E5E-131BA81C39E6
Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 1026047 1024000 500M EFI System
/dev/nvme0n1p2 1026048 17410047 16384000 7.8G Linux swap
/dev/nvme0n1p3 17410048 488392031 470981984 224.6G Linux filesystem